JPS60198823A - Ion beam etching method - Google Patents

Abstract

PURPOSE:To obtain an etching method which has a high selectivity ratio of etching rates and provides a vertical cross section with reduced damages, by etching Si in the atmosphere of fluorine gas or in a vaccum with the radiation of ion beams having low acceleration energy as well as the radiation of ultraviolet rays. CONSTITUTION:A material 31 of Si, SiO2 and the like is disposed within a vacuum device 30 into which fluorine gas 33 is introduced through a gas inlet tube 32 provided on the device 30. Under this condition, the material 31 is irradiated with ultraviolet light beams 35 from an ultraviolet radiation source 34 provided obliquely outside the device 30 through a window 36. The Si material 31 whose electronic state is thus excited is irradiated with ion beams 38 from an ion source 37 provided directly over the device 30 so that the Si is etched thereby. The SiO2, however, is not etched because it absorbs no ultraviolet rays 35. Since the ion beams 38 are applied vertically to the cross section of the material, it can be etched vertically in the cross section without causing side etch. Few defects are produced because low acceleration energy is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion beam etching method used in an electronic device manufacturing process.

[Prior art and its problems]

Conventionally hM, the etching process in the child device manufacturing process tends to shift from wet etching to dry etchingsb, and the technology is, for example, J, L,
Vossen F) J, Electrochem.
Soc, Vo1126.1979, P3j9~P3
24, r Glow Discharge Phe
Nomena in Plasma Etchinga
and Plasma Deposition J (Glow Discharge in Plasma Etching and Plasma Deposition) by C, J, Mogab, A, C, Aola.
ms and D, L, Flam to J, Appl,
Phys, Vol 49, 1979, P 37
96~P3803 r Plasma elching
of St and 5i02 J (St.

Parallel plate dry etching using high frequency discharge according to a paper published under the title ``Plasma etching of S 102'', and fi, J, 5harp, J, ni, G,
Pan1tzand D, M, Mattox J)
J, Vac, Sci, Technol vo116.1
979, rAppl Ic on P1879-P1882
ation of a Kaufman ton 5o
source to IOW energy tonero
Examples include ion beam etching in a paper published under the title ``Ion Etching with a Low Ion Energy Kafmann Type Ion Source''. In these dry etching methods, gas molecules containing nitrogen such as fluorine and chlorine are used.

St
This is to advance the etching process.

However, when manufacturing electronic devices, these molecules, atoms, radicals, and ions are also adsorbed onto SIO□.
irradiated. Furthermore, since etching progresses with the addition of physical impact, in the conventional etching method, the etching rate selectivity of Si, 5i02 is determined by the chemical reactivity with two atoms, radicals, and ions 81 and 5102. It will be brought about only by difference.

For this reason, the conventional method has the disadvantage that a high selectivity cannot be obtained. In the case of a parallel plate type device or a plasma etching device, the etching rate selectivity of Sir 5i02 was about 10 to 15 times that of S S O2 at most under etching conditions where a vertical etched cross section was obtained. In a parallel plate type device, if the gas is selected, a selection ratio of 60 times can be achieved, but in that case, the side etch under the mask is large and a vertical etched cross section cannot be obtained. In ion beam etching, side etching under the mask is less likely to occur, but the physical sputtering effect becomes stronger and the selectivity decreases. Furthermore, in general, ion beam etching requires high ion acceleration energy of 500 eV to 1 keV, so that a lot of damage is caused to the sample due to ion bombardment.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an etching method for dry etching of Sl, which has a high etching rate selectivity, has a vertical etching cross section, and causes less damage due to etching.

[Structure of the invention]

The present invention deals with S in a fluorine gas atmosphere or in a vacuum state.
This is an ion beam etching method characterized in that etching is carried out by irradiating ultraviolet rays and a low energy accelerated ion beam to etching.

[Detailed explanation of the configuration]

In the present invention, by adopting the above-mentioned configuration, the problems of the prior art in which the etching rate selection ratio is low, the problem in which damage remains on the object to be etched, and the problem in which the etching cross section is not vertical can be solved. resolved at the same time.

First, St and SiO2 in the etching apparatus are irradiated with ultraviolet light in the wavelength range of 200 nm to 420 nm. Graphs showing optical absorption and transmission of St and SiO□ in this wavelength range are shown in FIGS. 1 and 2. FIG. 1 shows the absorption coefficient of Si, where the horizontal axis is the wavelength (nm) and the vertical axis is the absorption coefficient (an-'). Absorption coefficient of Si 11
has a peak in this wavelength region and exhibits a large deviation overall, whereas in this wavelength region, the absorption coefficient of S i O2 is approximately O (<1++-1). Also, Figure 2 shows S
It shows the transmittance at t 02, and the horizontal axis is the wavelength (nm).
, the vertical axis is the transmittance (ch). 21 is the transmittance of S 1o2, whereas in this wavelength range, the transmittance of St is almost 0 (correspondence). As is clear from Figures 1 and 2, in the wavelength range of 200 nm to 420 nm, SL has a large absorption, but 5iO7 is almost transparent, so ultraviolet irradiation in this region excites only the electronic state of Si. Now, this creates two molecules of gas' atoms.

It can assist only St in reaction with radicals and ions.

Next, an ion beam is irradiated onto the St 5102 during ultraviolet 818 irradiation with an acceleration energy of 5 Q eV to 200 eV, which is lower than usual, to perform etching. S
For t, the acceleration energy of the ion beam is 50 eV to 200 e due to the assistance of ultraviolet irradiation.
A sufficient etching rate can be obtained even with a small value of V, and the etching rate for S102 is small because there is no absorption of ultraviolet rays and the acceleration energy of the ion beam is low. Further, even if the acceleration energy of the ion beam is as low as this, the etching cross section is almost vertical as in the case of 1 keV acceleration, and side etching under the mask is hardly observed. Furthermore, since the acceleration energy is low, damage caused by ion bombardment to the ion beam irradiation surface is extremely small.

In this ultraviolet assisted ion beam etching, fluorine gas is introduced into the etching equipment and etching is performed using an ion beam such as argon in an active fluorine gas atmosphere, and ion beam etching is performed without introducing any gas into the etching equipment. Two methods are possible: etching by etching only. In the former case, the etching rate is higher than in the latter case, but Si, S
In the case of i02, some contamination occurs, and in the latter case, conversely, contamination is small but the etching rate is small.

As described above, the ultraviolet-assisted ion beam etching according to the present invention has a high etching rate selectivity for St, 5i02, the etching cross section is vertical, there is less side etching under the mask, and etching can be performed with less damage caused by ion bombardment. becomes.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows a first embodiment of the present invention. St.

A sample 31 of 5IO2 is passed from the gas introduction pipe 32 to the vacuum device 30.
It is placed in an atmosphere of fluorine gas 33 introduced inside. For this sample 31, the ultraviolet rays 3 emitted from the ultraviolet source 34
5 through window 36.

An ion beam 3 is applied from an ion source 37 to a sample 31 in which the electronic state of St is excited by irradiation with ultraviolet rays 35.
When 8 is irradiated with low acceleration energy, S in the excited state
t is easily etched. child.

On the other hand, since S102 does not absorb ultraviolet rays, the electrons are returned to the ground state and are etched away. Furthermore, since this etching is ion beam etching in which ions are bombarded from a direction perpendicular to the sample surface, the etched cross section of the sample 31 is vertical, and side etching under the mask is hardly observed. Furthermore, since the acceleration energy of the ion beam 38 is low, defects caused by ion bombardment that are created on the ion beam irradiated surface of the sample 31 during etching are reduced.

Furthermore, adsorption of the fluorine gas molecules 33 onto the surface of the sample 31 has the effect of increasing the etching rate.

FIG. 4 shows a second embodiment of the invention. si.

A sample 41 of 5IO2 is passed from the gas introduction pipe 42 to the vacuum device 40.
It is placed in an atmosphere of fluorine gas 43 introduced therein. For this sample 41, ultraviolet light 45 emitted from the ultraviolet source
When irradiating the ultraviolet rays through the window 46, if it is not possible to set the ultraviolet ray source 34 in the position of the ultraviolet ray source 34 shown in FIG. Ultraviolet rays 4 emitted from an ultraviolet source 44 placed in
5 is reflected and then irradiated onto the sample 41. The sample 41 in which the electronic state of St has been excited in this manner is etched by irradiating the ion beam 48 from the ion source 47 in the same manner as in the first embodiment shown in FIG.

In this case as well, St in the excited state is etched with good selectivity at a high etching rate relative to 5102, and the etching cross section is vertical and there is little damage due to ion bombardment.

〔Effect of the invention〕

FIG. 5 shows the etching rate selectivity of Si, 5102 by the etching method of the present invention and the etching rate selectivity by the conventional ion beam etching method without ultraviolet irradiation. The horizontal axis of FIG. 5 is J [fluorine partial pressure in the empty device ~ the vertical axis is the ratio of the etching rate of St to the etching rate of 3102 R(St)/R(S i 02 )
It is. In both cases 51, 52, and 53, argon gas is introduced into the ion source in vacuum to increase the vacuum pressure to 8.
It is set to OX 10 Torr. 51 is Rokuto BB Kashitsuji F? In the case where fluorine gas is further introduced from the gas inlet tube into the vacuum apparatus, and ion beam etching is performed at 100 eV acceleration while irradiating the sample with ultraviolet rays in the fluorine gas atmosphere. This is the etching rate selection ratio.

52 is the etching rate selectivity when ion beam etching is performed at 1 keV acceleration in a fluorine gas atmosphere by further introducing fluorine gas from a gas introduction tube into a vacuum apparatus with an argon atmosphere, and No irradiation was performed. 53 is the etching rate selectivity when ion beam etching is performed at 200 eV acceleration while UV irradiation is performed in a vacuum apparatus with a sialbone atmosphere according to the method of the present invention, and fluorine gas is not introduced. At zero, that is, at 53, the fluorine partial pressure is zero. From the comparison of 51 and 52, the ultraviolet assisted ion beam etching in a fluorine atmosphere according to the present invention shown in 51 has a much higher etching rate than the ion beam etching in a fluorine atmosphere by the conventional method shown in 52. It can be seen that the effect of ultraviolet irradiation according to the present invention is extremely large. In addition, the etching rate selectivity when fluorine is used in ultraviolet assisted ion beam etching according to the present invention shown in 53 is also ＼
Although it is inferior in the case of 51 using fluorine, the selection ratio is higher than that of the conventional method, and it can be seen that the effect of ultraviolet irradiation is tremendous.

Furthermore, in the ultraviolet assisted ion beam etching of 51.53 according to the present invention, although the acceleration energy of the ions is low, the etching cross section is vertical and there is an underside as in the case of ion beam etching with high acceleration energy of 52 according to the conventional method. There wasn't much sex. In addition, in the case of 51°53 according to the present invention, the acceleration energy of the ions is lower than in the case of 52 according to the conventional method, so the damage caused by the ion gr1 bombardment on the ion irradiation surface is extremely small.
The effects of the present invention were obvious.According to the above-mentioned details, according to the present invention, 5I02 of St.
It is possible to increase the etching rate selectivity for
Furthermore, it is possible to perform etching with a vertical etching cross section and less damage caused by ion bombardment. Therefore, when the present invention is used in dry-grossing processes for manufacturing electronic devices, its effectiveness will be great.

[Brief explanation of drawings]

Figure 1 shows the wavelength distribution of the absorption coefficient of si, Figure 2 shows the wavelength distribution of the transmittance of S10□, and Figure 3 shows the wavelength distribution of the absorption coefficient of Si.
FIG. 4 is a cross-sectional view of a vacuum device showing a first embodiment using the etching method of the present invention, and FIG. 5 is a cross-sectional view of a vacuum device showing a second embodiment using the etching method of the present invention. is the St. according to the present invention. FIG. 4 is a diagram comparing the etching rate selectivity of 5in2 with the etching rate selectivity of a conventional method. 30, 40... Vacuum device, 31.41... Sample,
32.42... Gas introduction tube, 33.43... Fluorine gas molecules, 34.44... Ultraviolet light source, 35.45...
・Ultraviolet light, 36.46...Window, 37.47...Ion source, 38.48...Ion beam, 49...Anti-i
mirror. Figure 1: Yorocho (Yogame) Figure 2: Yorocho (Question)

Claims (1)

[Claims] (1) S in a fluorine gas atmosphere or in a vacuum state
An ion beam etching method characterized in that etching is carried out by irradiating an ion beam with ultraviolet rays onto the etching surface.